I headcanoned that when the Tomb of Sargeras is sealed, the spirits that were trapped from the initial assault on the Broken Shore were freed. Well this meant that Dasacht’s spirit was finally freed. But since he was/is a Warrior, he is being called to the Halls of Valor, though Dasora would be able to see him whenever she goes there, it won’t feel the same to her. So she is reluctantly saying goodbye.

details:
https://sta.sh/0z6z0glkskg